My pv journey is back on!

[1201]

My Solar PV journey is officially ending

or at least going on a very long Hiatus. So I built a passive solar house- the roof is 35° slope facing 4° west. no penetrations, no shading. I built it to be perfect for solar panels. BUT, net metering ended two months ago before I could get in and I have spent the last two months trying to...

diysolarforum.com

I had decided not to go solar due to the cost vs benefits. Well, after being on here a while and seeing some great deals, and doing endless spreadsheets and calcations, the decision has been rescinded! ?

I decided to do an offgrid system and use all my production(the house will still be fully on the grid)

So far I've purchased:
Two lv6048s for less than $2k
12kw of pv panels for $5500
43kwh of batteries for $4800
25 unirac rm10s for $400 that I won't use yet but may in the future, for expansion.

Total cost after tax credit should be about $12500

And looking at annual savings of almost $2000 t current energy prices, And, I no longer have to spend big bucks on a wood stove for when we have power outages in January, or a large generator just to run my well pump so I have water. So all in all I was able to make it make sense.

 

[timselectric]

Welcome to the addiction. lol

 

[1201]

Welcome to the addiction. lol

Yeah it's going to be bad lol ?

 

[RV10flyer]

My Solar PV journey is officially ending

or at least going on a very long Hiatus. So I built a passive solar house- the roof is 35° slope facing 4° west. no penetrations, no shading. I built it to be perfect for solar panels. BUT, net metering ended two months ago before I could get in and I have spent the last two months trying to...

diysolarforum.com

I had decided not to go solar due to the cost vs benefits. Well, after being on here a while and seeing some great deals, and doing endless spreadsheets and calcations, the decision has been rescinded! ?

I decided to do an offgrid system and use all my production(the house will still be fully on the grid)

So far I've purchased:
Two lv6048s for less than $2k
12kw of pv panels for $5500
43kwh of batteries for $4800
25 unirac rm10s for $400 that I may or may not use.

Total cost after tax credit should be about $12500

And looking at annual savings of almost $2000 t current energy prices, And, I no longer have to spend big bucks on a wood stove for when we have power outages in January, or a large generator just to run my well pump so I have water. So all in all I was able to make it make sense.

Production in January can be 4% of my max summer production. Hence the reason I have installed so much PV.

 

[1201]

Production in January can be 4% of my max summer production. Hence the reason I have installed so much PV.

4% whoa! So how much pv do you have?

 

[timselectric]

The goal is a crapton. But this takes time. lol

 

[1201]

The goal is a crapton. But this takes time. lol

Lol. Not for me. I think my head would hurt if I started seeing a bunch of unused power potential in the summer

 

[EastTexCowboy]

Production in January can be 4% of my max summer production. Hence the reason I have installed so much PV.

I was just thinking along the same lines. I don't think mine is a bad as 4%, but it's way, WAY less than summer production. If you have grid for backup then you're fine, but I certainly wouldn't depend on just solar for heat in the winter.

 

[EastTexCowboy]

4% whoa! So how much pv do you have?

Oh, and welcome back to the insanity!

 

[Crowz]

You never truly leave and there is no cure

 

[RV10flyer]

4% whoa! So how much pv do you have?

50k plus or minus. Woodburner and 10kW LP gen for backups. Shouldn’t need to use gen at all and wood burner below 20F. I’ll know the answer come Jan/Feb.

 

[1201]

Oh, and welcome back to the insanity!

I never left lol. I can't count how many endless hours I spend on this and other solar boards lol

 

[1201]

You never truly leave and there is no cure

This.

50k plus or minus. Woodburner and 10kW LP gen for backups. Shouldn’t need to use gen at all and wood burner below 20F. I’ll know the answer come Jan/Feb.

50kw of pv? Wowch!

 

[Hedges]

I decided to do an offgrid system and use all my production(the house will still be fully on the grid)

Will you run loads off batteries until they are drained then transfer-switch back to grid?
Or charge batteries until they are full, then curtail production and leave it's potential wasted?

One approach is to have grid recharge batteries as needed, rather than transfer switch.
I think the goal would be to aim for around 50% SoC, so there is power for loads and capacity to store production.

"Chargeverter" would be a way to do that, not sure about the SoC controls.
For more money, one inverter can be assigned that duty, and is available as a spare inverter.

You can get away with cycling lithium batteries because they can take daily cycles and still have many years life.
Lead-acid allows a fraction as many deep cycles.

A different type of inverter, in my case SMA AC coupled, others like Schneider with DC coupling, are able to blend AC from PV with AC from grid, so battery doesn't cycle. But they do have to either export to grid or curtail PV production for no cycling.
You need some cycling of battery to avoid both export and curtailing.

 

[1201]

Will you run loads off batteries until they are drained then transfer-switch back to grid?
Or charge batteries until they are full, then curtail production and leave it's potential wasted?

Goal is to use pv during the day to power loads and charge the battery, and then switch back to grid sometime during the night when the battery hits a certain soc(maybe 20%?)

One approach is to have grid recharge batteries as needed, rather than transfer switch.
I think the goal would be to aim for around 50% SoC, so there is power for loads and capacity to store production.

I've strongly considered that but I think it's quite a large energy penalty no? Say 10kwh from grid to battery at 90% efficiency (I don't know the actual number) and then 90% efficiency from battery back to grid, so 81% efficiency overall which means about 2.3kwh penalty per 10kwh of production.

I might still the hip doing it this way though and I don't know if my numbers are accurate


Oh and when I say house is fully on grid, means that I'm not moving my clothes dryer or range or bedrooms(just lights and fan -don't want any flicker)to off grid setup

 

[Hedges]

Maybe build the system with an AC charger as a UPS having PV, connect critical loads you always want powered.
Then have a few small transfer switches for other loads, especially loads that don't care about a glitch or phase jump. Move those loads between grid and UPS when you have surplus. Electric water heater is a good one because it can be tuned to various wattage and run for hours. Clothes dryer can be converted to 120V for 1/4 the wattage of heating element. Haven't tried, but could maybe split motor and heating element to different 120V phases.

Some people say refrigerators can lock up if switched out of phase, but I'm more inclined to believe only if they stop spinning then power up without pressure draining. Same for A/C.

Yes, gotta compare inefficiencies to lost production, could easily exceed. And consider wear and tear.
HV DC to AC runs in the 96% to 99% range. 48V battery to AC in the 90% to 96% range.
Lead-acid batteries consume significant percentage. Lithium supposedly not much.

But one guy observed actual round-trip efficiency of lithium based system was 81%, twice the loss he expected.
I'm inclined to attribute that to poor power factor of loads. Lots of non-PFC SMPS, each taking big gulps of current at peak AC voltage rather than drawing a sine-wave current. Losses go as square of current, so much more power dissipation in transistors and inductors compared to resistive loads (or European model products with good power factor.)

My System Efficiency is 81.3%. Prove me wrong or show me your math.

I just did a post about how my solar system performed over the last 159 days and I calculated my system efficiency which came out to a fairly abysmal 81.3%. So how did I calculate the efficiency? I measured my actual load using Emporia Vue inside my main panel. I have compared its readings to...

diysolarforum.com

Using off-grid inverter means saving hardware cost vs. grid-interactive and net metering (which may or may not be available to you.)
My backup system for now has a load-shed relay for the entire house. Want to eventually shed/add loads according to surplus generation.

 

[webbbn]

Clothes dryer can be converted to 120V for 1/4 the wattage of heating element. Haven't tried, but could maybe split motor and heating element to different 120V phases.

Is that suggestion to minimize max power requirements, or to try to make it more efficient. It makes sense that it would decrease the peak power requirements, but it seems like it would be overall less efficient. I would also imagine that the motor is 240V. Even if you had split-phase available, I don't know why you would put in a motor that only ran on one phase, and I believe the standard 30A dryer outlet only has L1,L2, and ground.

 

[OffGridForGood]

TOU Rates?
If your area has TOU-utility rates, I find it advantageous during Nov-Dec to let the PV collect what they can each day, then top up the ESS at night on low Time of Use rate to bring ESS to 100%, (in MPP settings there is one called "FUL" {full} so you can set the inverters to control charging up to 100% at night and then switch automatically back to "SBU" (solar battery utility) ready for the next morning).
On days with good solar, the night-time charge is very little energy/cost, and on crappy days it is more, but at the lowest utility rate available. For me, being out in the sticks, power outages are pretty common during winter (snow-covered trees like to fall on power lines it seems) so the charging up each night generally means I have my ESS pretty full when the utility drops out. Also the larger the difference in TOU rates, the more sense this makes to load-shift using the batteries.

To set up control for the TOU charging I use a programable HWT-Timer to cut off the Utility during on-peak time of day. Set the inverter to switch to 'charge battery from utility at a relatively high SOC like 53v, but when the inverter doesn't have the utility available it remains on battery/PV waiting. When the TOU rate comes up, my timer control switches on the utility - and the inverter immediately switches to charging until it hits that "ful" setting then it switches back to battery. In the early morning when TOU rate ends, the timer cuts off the utility and the inverters run off battery even while lower than the SOC setting I used, again the inverters are just waiting for utility to be available.

My solar set up is in the shop (next door to my home) and originally charging at night also meant the shop is basically just in heating mode (low electrical load) so one thing I noiced while adding more and larger loads from the house onto the shop solar - if the inverters are charging the ESS they are also in pass-through mode, so you don't really want to be charging and running the electric dryer/HWT all at the same time. There can be good reasons to set the control of the utility becoming available to midnight or some time of day with low use. A chargeverter would be a better option likely, set it to charge the ESS when utility is available, then use the HWT timer control to cut off power to the chargeverter when TOU rates are high. At least this is what I am thinking, not sure if the chargeverter will work this way, ie once power is cut off, will it need to be switched on, or will it come on as soon as power is available. I may need to think about a DC relay instead, ie the chargeverter on 'all the time' but the DC connection controlled by timer. I have to get my hands on a chargeverter and test it out.

 

[OffGridForGood]

Is that suggestion to minimize max power requirements, or to try to make it more efficient. It makes sense that it would decrease the peak power requirements, but it seems like it would be overall less efficient. I would also imagine that the motor is 240V. Even if you had split-phase available, I don't know why you would put in a motor that only ran on one phase, and I believe the standard 30A dryer outlet only has L1,L2, and ground.

I checked an my dryer motor is 120 and the heating element is 240.
The plug is four prong - L1 L2 N G - oh and the controls circuits are fed with 120v too.

 

[Hedges]

Is that suggestion to minimize max power requirements, or to try to make it more efficient. It makes sense that it would decrease the peak power requirements, but it seems like it would be overall less efficient. I would also imagine that the motor is 240V. Even if you had split-phase available, I don't know why you would put in a motor that only ran on one phase, and I believe the standard 30A dryer outlet only has L1,L2, and ground.

To minimize max power requirements, better work as a load on modest off-grid system to utilize available PV production.

Peak power of element is 1/4 as much at 120V, but drying doesn't take 4x as long. The on/off duty ratio varies to maintain thermostat.

Traditionally electric dryers in the US had a 3-wire cord, L1, L2, G. The 1/4 HP motor and controls ran off 120V, using G as neutral. The heating element ran off 240V L1/L2, and one of those could simply be connected to N for 120V operation. I often put a standard 15A 120V plug on them.

I wanted to use GFCI because my laundry is outdoors. I converted to 4-wire 120/240V plug. Even though I moved a neutral wire from ground to N, some current in ground still tripped it. After a couple tries I finally managed to move the other offending return wires from chassis to N and it works fine. I have 2-pole GFCI breaker feeding dryer outlet, and GFCI receptacle for washer. (have sometimes used differently with 240V washer.)

It may be some newer models use 240V for motor.